Alarm switch



u y 1959 R. G. JOHNSTON 2,897,307

ALARM SWITCH Filed April 29, 1958 I H ,w" I /7- 2.1 /'2 /9 /7) g BY IN V EN TOR. ROBERT 6. JOHNSTON United States Patent ALAIRM SWITCH Robert G. Johnston, Youngstown, Ohio Application April 29, 1958, Serial No. 731,783

3 Claims. (Cl. 200-6133) This invention relates to an alarm switch and more particularly to a simple inexpensive device that can be used to actuate audible and/or visual alarms by closing an electric circuit.

The principal object of the invention is the provision of an alarm switch that may be installed in a room or other enclosure and connected to a thread or string stretched across said room or enclosure so that a person entering said room or enclosure and breaking said thread or string will actuate said alarm switch.

A further object of the invention is the provision of an alarm switch that may be formed of a few simple inexpensive parts and which will function efficiently and unfailingly when actuated.

A still further object of the invention is the provision of an alarm switch including a contact guide and circuit terminals for receiving a weight having a conductive surface.

A still further object of the invention is the provision of an alarm switch of small size that may be mounted on a supporting wall surface adjacent a power source and alarm bell or light or the like.

The alarm switch disclosed herein comprises a single inexpensive device which may be used to originate an audible or visual alarm or both upon the breaking of a thread or string connected therewith and stretched across a room or an enclosure or through several rooms. The device is particularly useful in protecting small business establishments and stores and the like from theft and damage from unauthorized persons entering such premises. The alarm switch may be formed from a few molded plastic parts and installed in electrical connection with a suitable power source and a hell or light.

With the foregoing and other objects in view which will appear as the description proceeds, the invention resides in the combination and arrangement of parts in the details of construction hereinafter described and claimed, it being the intention to cover all changes and modifications of the example of the invention herein chosen for purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.

The invention is illustrated in the accompanying drawing, wherein:

Figure 1 is a side elevation of the alarm switch showing an alarm connected therewith and an actuating thread extended therefrom.

Figure 2 is a vertical section on line 2-2 of Figure 1.

Figure 3 is a horizontal section on line 3-3 of Figure 2.

Figure 4 is a vertical section of a portion of the device shown in Figure 2 showing the circuit closing portion thereof in circuit closing position.

By referring to the drawings and Figure 1 in particular it will seem that a supporting wall surface is indicated by the numeral and a base portion 11 of an alarm switch has been secured thereto as by fasteners 12. The

base portion 11 supports a cylindrical body member 13 which in turn is provided with a conical cap 14 having a central opening 15 at the apex thereof. By referring to Figure 2 of the drawings which is a vertical section on line 2-2. of Figure 1 it will be seen that a weight 16 preferably of conical shape is positioned in the cylindrical body 13 and is movable vertically therein and is attached to and suspended by a thread 17 which extends upwardly through the opening 15 in the conical cap 14 and outwardly therefrom as seen in Figure l of the drawing. In a typical installation the thread 17 extends across and/or around a room or other area to be protected and is passed through several eyelets 1818. The outermost end of the thread 17 is provided with a hook 19 which is secured to an eyelet 20. The length of the thread 17 is such that when hook 19 is engaged in the eyelet 20 the weight 16 will be elevated in the alarm switch as shown in Figure 2. When the thread 17 is broken the weight 16 drops into the position shown in the broken lines in Figure 2 and in solid lines in Figure 4. The base portion 11 of the alarm switch has a plurality of upstanding guides 2121 formed integrally therewith as seen in Figures 2, 3 and 4 of the drawings.

The base portion 11 also supports a pair of upstanding prongs 22-22 which are preferably formed of spring bronze with offset apertured sections 23-23 at their lower-most ends by means of which the same are secured to the base portion 11 by fasteners 2424. Electric circuit wires 25 and 26 are secured one to each of the fasteners 24-24 and establish electrical connection with the prongs 2222. The circuit wires 25 and 26 extend as illustrated on Figure 1 to a power source and alarm device such as a transformer 27 and a bell ringing mechanism 28. Circuit wire 2? connects the bell ringing mechanism 28 with the transformer 27 to complete the circuit and the transformer 27 is provided with a power cord 30 for connection with a conventional source of volt electric current. it will be seen by again referring to Figures 2, 3 and 4 of the drawings that when the thread 17 is broken the weight 16 will move downwardly and engage the upper angular ends of the prongs 22-22 as well as the upper angular ends of the guides 21-21 and as the prongs 2222 are slightly longer and higher than the guides 21--21 and the weight to comprises a conductor an electric circuit will be completed from the transformer 27 through the alarm switch to the bell ringing mechanism 28 whereby an audible alarm will be sounded.

It will occur to those skilled in the art that rather than the bell 23 a light may be used and that both a bell and a light may be employed as desired. It will also occur to those skilled in the art that a relay may be incorporated in the circuit between the power source 27 and the bell 28 so that the bell 28 will continue to be energized even though the weight 16 in the alarm switch is elevated.

By referring to Figure 4 of the drawings it will be seen that part of the weight 16 has been broken away to indicate that same is formed of metal. It will occur to those skilled in the art that weight 16 can be formed of other material and provided 'with a metallic conductor shell.

it will thus be seen that an alarm switch has been disclosed which meets the several objects of the invention and having thus described my invention, what 1 claim is:

1. An alarm switch comprising an enclosure including a base portion having a plurality of spaced upstanding guides thereon, a pair of spaced upstanding metal prongs on said base portion, said guides and prongs positioned in a circumferential arrangement, a weight suspended in said enclosure above said metal prongs and guides,

means suspending said Weight comprising a frangible flexible elongated member extending outwardly from said enclosure and secured in stationary position at its outermost end, said weight having a metal surface.

2. An alarm switch comprising a base having a pair of oppositely disposed vertical guides thereon and a pair of oppositely disposed upstanding prongs secured thereto in spaced circumferential relation to one another, a body member on said base having a portion defining a central orifice, a thread positioned through said orifice and ex- 10 body member on said base comprises a cylindrical body member having a conical cap apertured at the apex thereof. I

References Cited in the file of this patent UNITED STATES PATENTS 630,671 Des Isles Aug. 8, 1899 1,902,578 Parsons Mar. 21, 1933 2,701,282 Berry Feb. 1, 1955 FOREIGN PATENTS 20,678 Great Britain Nov. 27, 1891 

